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LCD Backlight Repair

LCD Monitors have become very popular with prices coming down, and screen sized growing. Those of us that have used LCD monitors for a while know that over time the backlight starts to dim and will eventually completely fail. Leaving you with some electronic scrap that you could sell on eBay for 35 bucks or so. Well for less than $20.00 and about a half hour of your time you can replace the backlight and rejuvenate that monitor to as good as new condition. So man the surplus scrounging wagon and head out to your local school surplus or eBay!

I have been using LCD monitors for years now, and unfortunately I have had the backlights in a couple of them fail. One failed due to the bulb, the second failed due to the power supply failing and hosing the bulb. I attempted to contact the manufacturers several times to try to get replacement parts, but the drones that work at Viewsonic or KDS gave me a canned response. “The model you have has been replaced with a newer model and is not supported any more”. almost every other month Viewsonic comes out with a new model that is faster refresh, or higher contrast ratio or something of the like…. so it has been totally imposable to get replacement parts. Couple that with the usual one year backlight warranty and you can see it can be good business for them to have a part that costs less them less than a dollar fail just after the warranty runs out. Well realizing that I am not the only one that has felt this frustration I decided to take matters into my own hands. I was surprised how easy and cheep it was to rescue my LCD monitors from the geek hacking bench.

The Monitor:
So first off you will need your monitor. Most LCD monitors are constructed the same way, with a cold cathode bulb as the back light source. A plastic sheet acts as a lens that refracts the light from the edge to the front of the screen and through the LCD panel. A small 12V inverter provides power to the bulb. As the bulbs get old they can have a hard time starting, lighting at all, flickering, or even putting out a strong pink colored light

The Replacemt Backlight:
Cold cathode bulbs can be hard to come by new and unused, and they can cost allot ordered from resale vendors. So we looked to case lighting for the source of our bulbs. Xoxide has an excellent selection of them with the inverter for about $9.00 and a couple bucks for shipping, and so does lcdparts.com. A good 15″ kit will provide a bulb for a 15″ monitor just fine! I have been able to find 17″ kits as well as 19″ kits. But most likely you wont have to replace your inverter, and that will save you a couple bucks.

The first step after you have all the parts you will need is to start the disassembly of your monitor. Remove the stand completely from the monitor and I recommend outright removing it from your work bench. These are often very heavy and are at least half of the weight of the monitor. If it was knocked over onto your work it could damage your project or the unsuspecting foot it was dropped onto.

With the back panel removed you can gain access to the bulb at the bottom of the monitor. Often in these monitors is some sheet metal that acts as shielding for the monitor. Remove the shielding carefully and you will have access to the inverter as well. if you have access to a grounding strap I recommend using it from this point out to reduce risks of damaging any of the circuit boards.

Now we deal with the case lighting. The cold cathode is incased in a plastic case to protect it and defuse the light. We will need to remove the casing very carefully. Most cold cathode tubes have mercury vapor in them this is very dangerous if it was broken. Avoided damaging the bulb at all costs as mercury vapor has been linked to brain damage and cancer. so be careful…. unless your some arch-villain with a diabolical plan.

Using a dremel tool and a cutting disk on the highest speed use the wheel to melt the plastic all the way around near the caped end with the leads coming out of it. Taking care not to cut to deep and possibly damaging the tube. Once separated use a blow dryer to heat up the glue in the cap with leads. When the glue gets hot it will become soft and allow you to pull the wired and bulb free. Some coaxing may be needed and maybe a bent paperclip to remove some glue before it will be freed. I strongly recommend doing this outside in the open air do if you mistakenly cut to deep or otherwise break the tube you can be relatively safe with good ventilation. Once removed the bulb is very fragile so take care with it not to hurt it. or it may hurt you in return.

Remove the reflector that holds the bulb from the LCD monitor carefully. Often there is a soft small clear plastic O’ ring that suspends the bulb in the reflector. If you can not salvage these you can use a few wraps of a thin strip of a good quality clear tape. Dispose of the old bulb, and mount the new bulb in its place. You may want to cut the end off of the old bulbs wires with enough slack to splice into the new bulb to match the plug of the inverter. Reinsert the reflector tray back into the monitor and secure it as it was originally. Finally attach the power to the inverter.

If you have a bad inverter remove the old inverter from the monitor. Using the new one you got with the kit, remove the plastic case the inverter is in with a razor or flat head screwdriver. Splice the ends of the leads it has to the power for the original backlight and attach it to the mounting point the old one was on as best you can. Often there is a simple way using the original screws and a hole in the new inverters board.

Before you reassemble your monitor power it up to verify that it lights up. If you had to replace your inverter your on screen controls will not likely work for brightness, but if you have a half descent video card you can do it in the video card settings if needed. Finally reassemble the monitor and reattach the monitor to the stand.

So for about $15.00 you can breath new life into that old monitor just gathering dust on your work bench. Yah there is some risks with the bulbs. But if your about your wit’s should do just fine.

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